RT9204CS Просмотр технического описания (PDF) - Richtek Technology

Номер в каталоге

Компоненты Описание

Список матч

RT9204CS

Dual Regulator - Standard Buck PWM DC-DC and Linear Power Controller

Richtek Technology 

COUNT = 1 COUNT = 2 COUNT = 3

4V

2V

0V

OVER LO AD

APPLIED

Preliminary

RT9204

Shutdown

Pulling high the SD pin by a small single transistor

can shutdown the RT9204 PWM controller as shown

in typical application circuit. Normally SD pin can be

floating because an internal 40µA current source will

pull low the SD shutdown pin voltage.

T0T1

T2

T3

TIME

Fig. 3

Applications Information

Inductor Selection

The RT9204 was designed for VIN = 5V, step-down

application mainly. Fig.4 shows the typical topology

and waveforms of step-down converter.

The ripple current of inductor can be calculated as

follows:

ILRIPPLE = (5V - VOUT)/L × TON

Because operation frequency is fixed at 600kHz,

TON = 3.33 × VOUT/5V

The VOUT ripple is

VOUT RIPPLE = ILRIPPLE × ESR

ESR is COUT capacitor equivalent series resistor

Table 1 shows the ripple voltage of VOUT: VIN = 5V

*Refer to Sanyo low ESR series (CE, DX, PX…)

The suggested L and C are as follows:

2µH with ≥ 1500µF COUT

5µH with ≥ 1000µF COUT

Q

VI

L

VL

D

C

R VO

C.C.M.

TS

Table 1

TON TOFF

VI - VO

VL

- VO

iL

µQ

µIL

IL = IO

iQ

IQ

iD

ID

Fig.4

VOUT

Inductor

1000µF (ESR = 53mΩ)

1500µF (ESR = 33mΩ)

3000µF (ESR = 21mΩ)

3.3V

2µH

5µH

100mV 40mV

62mV 25mV

40mV 16mV

2.5V

2µH

5µH

110mV 44mV

68mV 28mV

43mV 18mV

1.5V

2µH

5µH

93mV 37mV

58mV 23mV

37mV 15mV

DS9204-00 February 2002

www.richtek-ic.com.tw

9

Share Link: